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18 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Low voltage x-ray tubes are generally fitted with windows made of ___________. |
Beryllium |
Beryllium allows all but the longest wavelength x-rays to pass through it |
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If it were necessary to radiograph a 7 inch thick steel product, what gamma-ray source would most likely be used? |
Cobalt-60 |
Cobalt is suitable for radiographing steel above 3-4 inches thick and has a rated penetrating power of 1.17 and 1.33 mev respectively. |
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A cobalt-60 gamma-ray source has an approximate practical thickness limit of ________. |
9 inches of steel or its equivalent |
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The absorption of gamma-rays from a given source when passing through matter depends on __________. |
The atomic number, density, and thickness of the matter |
All effect the absorption of both gamma and x-rays |
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The fact that gases, when bombarded by radiation, ionize and become electrical conductors make them useful in ____________. |
Radiation detection equipment |
The phenomenon is used in pocket dosimeters and other detection equipment |
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The uneven distribution of developed grains within the emulsion of a processed x-ray film causes the subjective impression of ___________. |
Graininess |
Also note the faster the film the larger the individual silver salts (grains). Thus fast film tends to be grainier. |
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Of the following, the source providing the most penetrating radiation is: A. Cobalt-60 B. 15 Mev x-ray betatron |
B. 15 Mev x-ray betatron |
A 15 Mev x-ray betatron is a linear accelerator whose beam strength is 12 times that of cobalt-60 (the next best penetrating of the two) |
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The gamma-ray intensity at one foot from a one curie source of radioactive cobalt-60 is nearest ____________. |
15 roentgens per hour |
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The specific activity of an isotopic source is usually measured in _________. |
Curies per gram |
The curies per gram is the measure of specific activity. One curie equals 37,000,000 disintegrations per second. |
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Which of the following isotopes has the longest half-life? A. Cobalt-60 B. Cesium-137 |
B. Cesium-137 |
Has a half-life of 30 years |
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An x-ray film having wide latitude also has, by definition _____________. |
Low contrast |
X-ray film with a narrow latitude by definition are high contrast |
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One method of reducing radiographic contrast is to_______. |
Decrease the wavelength of the radiation used. |
Shorter wavelength x-rays are more penetrating but less photographically active and produce high contrast radiographs |
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Thin sheets of lead foil in intimate contact with x-ray film during exposure increase film density because ______________. |
They emit electrons when exposed to X and gamma radiation which help darken the film. |
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A good cobalt-60 radiograph is made on a 3 in steel casting using an exposure time of 10 minutes and a source-to-film distance of 36 inches. It is necessary to change the source-to-film distance to 24 in, what exposure time would produce a similar radiograph if all other conditions remain the same? |
4.4 minutes |
3 ft squared equals 9, and 2 ft squared equals 4. 4/9 = 4/9 x 10 = 4.444... |
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When sharp, black bird-foot shaped marks which are known not to correspond with any discontinuities appear at random on radiographs, they are probably caused by _________. |
Static charges caused by friction. |
The electrical discharge of static electricity exposes crystals. |
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The range of thickness over which densities are obtained that are satisfactory for interpretation is a measure of the __________. |
latitude of a radiograph |
the range of thickness over which densities are satisfactory for interpretation is known as latitude. |
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Almost all gamma radiography is performed with __________. |
Iridium-192 or Cobalt-60 |
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Images of discontinuities close to the source side of the specimen become less clearly defined as __________. |
the thickness of the specimen increases |
The increase in material between the discontinuity and the film reduces the definition |
